A wind turbine generator is a device that generates electricity by causing a rotor head equipped with wind turbine blades to rotate in response to a wind force and then increasing the speed of the rotation using a speed-increasing gear.
The aforementioned rotor head is disposed on the top of a wind turbine tower (referred to as “tower” hereinafter), is attached to an end of a yawable nacelle, and is supported in a rotatable manner about a rotation axis extending substantially in the horizontal direction.
In general, the aforementioned wind turbine tower often employs a steel monopole type that uses a cylindrical shell. In such a steel-monopole-type tower, since the cylindrical shell are composed of steel serves as the main reinforcement member, the cross-sectional efficiency is enhanced by increasing the outer diameter of the shell. Therefore, in a steel-monopole-type tower, it is desirable to maximize the outer diameter of the shell within a range allowing a reduction in weight.
On the other hand, a proposed example of a tower for a wind turbine generator employs a space-frame structure in which at least one of a longitudinally extending member and a diagonally extending member is made to serve as a damping member for damping an anti-cyclic gust or sustained high-speed wind (for example, see Patent Citation 1).
Patent Citation 1:    Japanese Translation of PCT International Application, Publication No. 2008-540918